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xen/gntdev: Add initial support for dma-buf UAPI

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Add UAPI and IOCTLs for dma-buf grant device driver extension:
the extension allows userspace processes and kernel modules to
use Xen backed dma-buf implementation. With this extension grant
references to the pages of an imported dma-buf can be exported
for other domain use and grant references coming from a foreign
domain can be converted into a local dma-buf for local export.
Implement basic initialization and stubs for Xen DMA buffers'
support.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
Oleksandr Andrushchenko 2018-07-20 12:01:48 +03:00 committed by Boris Ostrovsky
parent 1d31456755
commit 932d656217
7 changed files with 349 additions and 0 deletions
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10
drivers/xen/Kconfig
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@ -152,6 +152,16 @@ config XEN_GNTDEV
help
Allows userspace processes to use grants.
config XEN_GNTDEV_DMABUF
bool "Add support for dma-buf grant access device driver extension"
depends on XEN_GNTDEV && XEN_GRANT_DMA_ALLOC && DMA_SHARED_BUFFER
help
Allows userspace processes and kernel modules to use Xen backed
dma-buf implementation. With this extension grant references to
the pages of an imported dma-buf can be exported for other domain
use and grant references coming from a foreign domain can be
converted into a local dma-buf for local export.
config XEN_GRANT_DEV_ALLOC
tristate "User-space grant reference allocator driver"
depends on XEN

1
drivers/xen/Makefile
View File

@ -41,5 +41,6 @@ obj-$(CONFIG_XEN_PVCALLS_BACKEND) += pvcalls-back.o
obj-$(CONFIG_XEN_PVCALLS_FRONTEND) += pvcalls-front.o
xen-evtchn-y := evtchn.o
xen-gntdev-y := gntdev.o
xen-gntdev-$(CONFIG_XEN_GNTDEV_DMABUF) += gntdev-dmabuf.o
xen-gntalloc-y := gntalloc.o
xen-privcmd-y := privcmd.o privcmd-buf.o

6
drivers/xen/gntdev-common.h
View File

@ -16,6 +16,8 @@
#include <linux/mmu_notifier.h>
#include <linux/types.h>
struct gntdev_dmabuf_priv;
struct gntdev_priv {
/* Maps with visible offsets in the file descriptor. */
struct list_head maps;
@ -33,6 +35,10 @@ struct gntdev_priv {
/* Device for which DMA memory is allocated. */
struct device *dma_dev;
#endif
#ifdef CONFIG_XEN_GNTDEV_DMABUF
struct gntdev_dmabuf_priv *dmabuf_priv;
#endif
};
struct gntdev_unmap_notify {

177
drivers/xen/gntdev-dmabuf.c Normal file
View File

@ -0,0 +1,177 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Xen dma-buf functionality for gntdev.
*
* Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <xen/xen.h>
#include <xen/grant_table.h>
#include "gntdev-common.h"
#include "gntdev-dmabuf.h"
struct gntdev_dmabuf_priv {
/* List of exported DMA buffers. */
struct list_head exp_list;
/* List of wait objects. */
struct list_head exp_wait_list;
/* This is the lock which protects dma_buf_xxx lists. */
struct mutex lock;
};
/* DMA buffer export support. */
/* Implementation of wait for exported DMA buffer to be released. */
static int dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
int wait_to_ms)
{
return -EINVAL;
}
static int dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
int count, u32 domid, u32 *refs, u32 *fd)
{
*fd = -1;
return -EINVAL;
}
/* DMA buffer import support. */
static struct gntdev_dmabuf *
dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
int fd, int count, int domid)
{
return ERR_PTR(-ENOMEM);
}
static u32 *dmabuf_imp_get_refs(struct gntdev_dmabuf *gntdev_dmabuf)
{
return NULL;
}
static int dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
{
return -EINVAL;
}
/* DMA buffer IOCTL support. */
long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv, int use_ptemod,
struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
{
struct ioctl_gntdev_dmabuf_exp_from_refs op;
u32 *refs;
long ret;
if (use_ptemod) {
pr_debug("Cannot provide dma-buf: use_ptemode %d\n",
use_ptemod);
return -EINVAL;
}
if (copy_from_user(&op, u, sizeof(op)) != 0)
return -EFAULT;
if (unlikely(op.count <= 0))
return -EINVAL;
refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
if (!refs)
return -ENOMEM;
if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
ret = -EFAULT;
goto out;
}
ret = dmabuf_exp_from_refs(priv, op.flags, op.count,
op.domid, refs, &op.fd);
if (ret)
goto out;
if (copy_to_user(u, &op, sizeof(op)) != 0)
ret = -EFAULT;
out:
kfree(refs);
return ret;
}
long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
{
struct ioctl_gntdev_dmabuf_exp_wait_released op;
if (copy_from_user(&op, u, sizeof(op)) != 0)
return -EFAULT;
return dmabuf_exp_wait_released(priv->dmabuf_priv, op.fd,
op.wait_to_ms);
}
long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
{
struct ioctl_gntdev_dmabuf_imp_to_refs op;
struct gntdev_dmabuf *gntdev_dmabuf;
long ret;
if (copy_from_user(&op, u, sizeof(op)) != 0)
return -EFAULT;
if (unlikely(op.count <= 0))
return -EINVAL;
gntdev_dmabuf = dmabuf_imp_to_refs(priv->dmabuf_priv,
priv->dma_dev, op.fd,
op.count, op.domid);
if (IS_ERR(gntdev_dmabuf))
return PTR_ERR(gntdev_dmabuf);
if (copy_to_user(u->refs, dmabuf_imp_get_refs(gntdev_dmabuf),
sizeof(*u->refs) * op.count) != 0) {
ret = -EFAULT;
goto out_release;
}
return 0;
out_release:
dmabuf_imp_release(priv->dmabuf_priv, op.fd);
return ret;
}
long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
struct ioctl_gntdev_dmabuf_imp_release __user *u)
{
struct ioctl_gntdev_dmabuf_imp_release op;
if (copy_from_user(&op, u, sizeof(op)) != 0)
return -EFAULT;
return dmabuf_imp_release(priv->dmabuf_priv, op.fd);
}
struct gntdev_dmabuf_priv *gntdev_dmabuf_init(void)
{
struct gntdev_dmabuf_priv *priv;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
return ERR_PTR(-ENOMEM);
return priv;
}
void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv)
{
kfree(priv);
}

33
drivers/xen/gntdev-dmabuf.h Normal file
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@ -0,0 +1,33 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Xen dma-buf functionality for gntdev.
*
* Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
*/
#ifndef _GNTDEV_DMABUF_H
#define _GNTDEV_DMABUF_H
#include <xen/gntdev.h>
struct gntdev_dmabuf_priv;
struct gntdev_priv;
struct gntdev_dmabuf_priv *gntdev_dmabuf_init(void);
void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv);
long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv, int use_ptemod,
struct ioctl_gntdev_dmabuf_exp_from_refs __user *u);
long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
struct ioctl_gntdev_dmabuf_exp_wait_released __user *u);
long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
struct ioctl_gntdev_dmabuf_imp_to_refs __user *u);
long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
struct ioctl_gntdev_dmabuf_imp_release __user *u);
#endif

31
drivers/xen/gntdev.c
View File

@ -48,6 +48,9 @@
#include <asm/xen/hypercall.h>
#include "gntdev-common.h"
#ifdef CONFIG_XEN_GNTDEV_DMABUF
#include "gntdev-dmabuf.h"
#endif
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
@ -566,6 +569,15 @@ static int gntdev_open(struct inode *inode, struct file *flip)
INIT_LIST_HEAD(&priv->freeable_maps);
mutex_init(&priv->lock);
#ifdef CONFIG_XEN_GNTDEV_DMABUF
priv->dmabuf_priv = gntdev_dmabuf_init();
if (IS_ERR(priv->dmabuf_priv)) {
ret = PTR_ERR(priv->dmabuf_priv);
kfree(priv);
return ret;
}
#endif
if (use_ptemod) {
priv->mm = get_task_mm(current);
if (!priv->mm) {
@ -616,8 +628,13 @@ static int gntdev_release(struct inode *inode, struct file *flip)
WARN_ON(!list_empty(&priv->freeable_maps));
mutex_unlock(&priv->lock);
#ifdef CONFIG_XEN_GNTDEV_DMABUF
gntdev_dmabuf_fini(priv->dmabuf_priv);
#endif
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);
kfree(priv);
return 0;
}
@ -1009,6 +1026,20 @@ static long gntdev_ioctl(struct file *flip,
case IOCTL_GNTDEV_GRANT_COPY:
return gntdev_ioctl_grant_copy(priv, ptr);
#ifdef CONFIG_XEN_GNTDEV_DMABUF
case IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS:
return gntdev_ioctl_dmabuf_exp_from_refs(priv, use_ptemod, ptr);
case IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED:
return gntdev_ioctl_dmabuf_exp_wait_released(priv, ptr);
case IOCTL_GNTDEV_DMABUF_IMP_TO_REFS:
return gntdev_ioctl_dmabuf_imp_to_refs(priv, ptr);
case IOCTL_GNTDEV_DMABUF_IMP_RELEASE:
return gntdev_ioctl_dmabuf_imp_release(priv, ptr);
#endif
default:
pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
return -ENOIOCTLCMD;

91
include/uapi/xen/gntdev.h
View File

@ -5,6 +5,7 @@
* Interface to /dev/xen/gntdev.
*
* Copyright (c) 2007, D G Murray
* Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
@ -215,4 +216,94 @@ struct ioctl_gntdev_grant_copy {
*/
#define GNTDEV_DMA_FLAG_COHERENT (1 << 1)
/*
* Create a dma-buf [1] from grant references @refs of count @count provided
* by the foreign domain @domid with flags @flags.
*
* By default dma-buf is backed by system memory pages, but by providing
* one of the GNTDEV_DMA_FLAG_XXX flags it can also be created as
* a DMA write-combine or coherent buffer, e.g. allocated with dma_alloc_wc/
* dma_alloc_coherent.
*
* Returns 0 if dma-buf was successfully created and the corresponding
* dma-buf's file descriptor is returned in @fd.
*
* [1] Documentation/driver-api/dma-buf.rst
*/
#define IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS \
_IOC(_IOC_NONE, 'G', 9, \
sizeof(struct ioctl_gntdev_dmabuf_exp_from_refs))
struct ioctl_gntdev_dmabuf_exp_from_refs {
/* IN parameters. */
/* Specific options for this dma-buf: see GNTDEV_DMA_FLAG_XXX. */
__u32 flags;
/* Number of grant references in @refs array. */
__u32 count;
/* OUT parameters. */
/* File descriptor of the dma-buf. */
__u32 fd;
/* The domain ID of the grant references to be mapped. */
__u32 domid;
/* Variable IN parameter. */
/* Array of grant references of size @count. */
__u32 refs[1];
};
/*
* This will block until the dma-buf with the file descriptor @fd is
* released. This is only valid for buffers created with
* IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS.
*
* If within @wait_to_ms milliseconds the buffer is not released
* then -ETIMEDOUT error is returned.
* If the buffer with the file descriptor @fd does not exist or has already
* been released, then -ENOENT is returned. For valid file descriptors
* this must not be treated as error.
*/
#define IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED \
_IOC(_IOC_NONE, 'G', 10, \
sizeof(struct ioctl_gntdev_dmabuf_exp_wait_released))
struct ioctl_gntdev_dmabuf_exp_wait_released {
/* IN parameters */
__u32 fd;
__u32 wait_to_ms;
};
/*
* Import a dma-buf with file descriptor @fd and export granted references
* to the pages of that dma-buf into array @refs of size @count.
*/
#define IOCTL_GNTDEV_DMABUF_IMP_TO_REFS \
_IOC(_IOC_NONE, 'G', 11, \
sizeof(struct ioctl_gntdev_dmabuf_imp_to_refs))
struct ioctl_gntdev_dmabuf_imp_to_refs {
/* IN parameters. */
/* File descriptor of the dma-buf. */
__u32 fd;
/* Number of grant references in @refs array. */
__u32 count;
/* The domain ID for which references to be granted. */
__u32 domid;
/* Reserved - must be zero. */
__u32 reserved;
/* OUT parameters. */
/* Array of grant references of size @count. */
__u32 refs[1];
};
/*
* This will close all references to the imported buffer with file descriptor
* @fd, so it can be released by the owner. This is only valid for buffers
* created with IOCTL_GNTDEV_DMABUF_IMP_TO_REFS.
*/
#define IOCTL_GNTDEV_DMABUF_IMP_RELEASE \
_IOC(_IOC_NONE, 'G', 12, \
sizeof(struct ioctl_gntdev_dmabuf_imp_release))
struct ioctl_gntdev_dmabuf_imp_release {
/* IN parameters */
__u32 fd;
__u32 reserved;
};
#endif /* __LINUX_PUBLIC_GNTDEV_H__ */